1. Field of the Invention
The present invention relates to a cordless telephone that can make a call through each of an independent system base station and an outdoor public system base station, and its communication method.
2. Description of the Related Art
In a second generation cordless telephone system, a digital cordless telephone of the system can be registered in advance on each of an outdoor public telephone communication system and an independent (private) telephone communication system to be used as a personal station (mobile station) of both the outdoor public telephone communication system and the independent telephone communication system.
Hereafter, in this specification, the outdoor public telephone communication system is merely referred to as an outdoor public system. The independent telephone communication system is intended to be used as a local facility, such as a home or a business building. Also, it is merely referred to as an independent system. The independent system implies a telephone communication system for the home and the business building.
FIG. 1 is a schematic configuration view showing such a second generation cordless telephone system as a whole. In the example shown in FIG. 1, two outdoor public system base stations 104, 106 are provided in the vicinity of an independent system base station 102 connected to a telephone line 101. A part of a service area (receiving region) 108 of the independent system base station 102 and a part of a service area 110 of the outdoor public system base station 104 overlap with each other. A service area 112 of the outdoor public system base station 106 does not overlap with the service area 108, and then overlaps with a part of the service area 110.
The independent system base station 102 and the outdoor public system base stations 104, 106 periodically transmit respective control signals. As shown in timing charts of FIGS. 2A and 2B, usually, a cordless telephone 114 intermittently receives these control signals 116, 118 in reception periods TR1, TR2 that are alternately repeated at in a certain period T. In addition, the control signal 116 is a control signal transmitted from the independent system base station 102, and the control signal 118 is a control signal transmitted from the outdoor public system base station 104.
The cordless telephone 114 searches the received control signals 116, 118 to then judge whether or not base station numbers of the independent system and the outdoor public system are included in the control signals 116, 118. A state in which the cordless telephone 114 carries out the judgment is referred to as a waiting state. Then, if the base station number of the independent system is included as the judged result, the cordless telephone 114 can make a communication between the cordless telephone 114 and the independent system base station 102 and can make a call through the independent system base station 102. If the base station number of the outdoor public system is included as the judged result, the cordless telephone 114 can make a communication between it and the outdoor public system base station, and can also make a call through the outdoor public system base station.
As shown in FIG. 1, if the cordless telephone 114 exists at a location A, the cordless telephone 114 receives at a time division the control signals from both the independent system base station 102 and the outdoor public system base station 104 to then search the base station numbers of the respective systems in the respective control signals. On the other hand, if the cordless telephone 114 exists at a location B, it can receive only the control signal from the outdoor public system base station 106, and can not receive the control signal from the independent system base station 102. Thus, the cordless telephone 114 can make only a call through the outdoor public system base station 106, since it can not search the base station number of the independent system.
By the way, if the cordless telephone 114 exists outside the service area 108, the cordless telephone 114 can not make a call through the independent system base station 102. Thus, it is possible to stop a waiting operation of receiving the control signal from the independent system base station 102 to search the base station number of the independent system base station 102. Accordingly, it is possible to reduce a consumption power in the cordless telephone 114 and suppress an exhaustion of a power supply battery of the telephone to thereby make a callable time longer.
However, the following trouble is induced if the waiting operation to the independent system is immediately stopped, merely because the cordless telephone 114 exists outside the service area 108. This trouble is that the call in the independent system can not be made although the cordless telephone 114 exists inside the service area 108 when the cordless telephone 114 exists relatively close to the service area 108 and immediately moves into the service area 108.
In addition, the following techniques are well known as the cordless telephone.
The following technique is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 7-240966). A cordless telephone has a first synchronizer synchronous with an outdoor public system and a second synchronizer synchronous with a home (independent) system, and is synchronous with the home system inside a service area for the home system, and is synchronous with the public system inside a service area for the public system. Then, it can be automatically switched by an independent/public switch. If the cordless telephone moves from the service area of one system to the service area of the other system, it is automatically synchronous with the system.
The following technique is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 8-79829). When a power supply of a mobile station is turned ON, when a mobile station in the waiting state carries out an outside area detection, or when the mobile station in the waiting state is registered on a public base station adjacent to a home/business facility system, an automatic mode setting manger causes a signal detector from the public base station and a signal detector from the home/business facility base station to detect the signals from the public base station and the home/business facility base station. Then, it sets a mode for a home/business facility mode if there is a communicable home/business facility base station, and sets a mode for a public mode if the home/business facility base station can not make a communication and further there is the communicable public base station, and then establishes an automatic mode setting in which a priority is set for the home/business facility mode and a location registration associated therewith.
The following technique is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 8-172666). Immediately after the mobile station moves inside a reception area of an identification symbol (CS-ID) of an independent radio base station (CS) that can be accessed as a cordless telephone or outside the reception area, an identification symbol (BS-ID) of a public radio base station (BS) that can be accessed as a portable telephone receiving an electric wave is stored in the mobile station as a boundary area. Then, the mobile station automatically switches (1) a cordless telephone mode of waiting an incoming signal from the CS in an area where the CS-ID can be received, (2) a portable telephone mode of waiting an incoming signal from the BS in an area where the BS-ID can be received except a boundary area, and (3) a boundary mode of waiting the incoming signals from both the BS and the CS in an area where the BS-ID of the boundary area can be received.
Moreover, the following technique is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 8-172666). The mobile station can store therein a system call symbol of an independent system that can be accessed by an intra-station and an enterpriser identification symbol of a public system and freely move in a radio zone of the independent system and the public system and also carry out a transmission and a reception.
A control signal, such as an incoming signal to the mobile station or the like, is transmitted at a frequency different for each system from the independent system base station (CS) and a plurality of public system base stations (BS), and also intermittently transmitted at a timing different for each CS and BS.
Each system waits for the incoming signal through the intermittent reception in time to an intermittent reception timing from each CS or the plurality of BSs. Typically, the mobile station is ready for the signal reception from the mobile communication system side and always waits for the incoming signal from the CS or the plurality of BSs through the intermittent reception. If the reception of the incoming signal through the intermittent reception can not be done because of the movement outside the radio zone and the like, it waits for the incoming signal through the intermittent reception by again matching the timing with the intermittent transmission from other CS or the plurality of BSs inside the system through a continuous reception within a certain period.
The following technique is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 9-70073). At a time of an independent mode operation, a registration of location information at a time of a public mode operation is cancelled, and information in relation to an independent radio zone is registered. In addition, at a time of the public mode operation, the registration of the information in relation to the independent radio zone is cancelled, and the location information of a radio communication terminal in relation to a public radio zone is registered. Then the database in which such predetermined information is registered or removed is searched, and the control of the reception and the transmission of an incoming call are carried out in accordance with the result.
The following technique is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 9-261755). An identification symbol of the public base station whose area reaches the independent base station is stored in a built-in memory of a micro computer. If a synchronization with any one of control channels of the public base station and the independent base station is not established, a state of alternately receiving the control channels of the public base station and the independent base station is set. If the reception of the control channel of the public base station establishes the synchronization with the control channel thereof, it is judged whether or not an identification symbol included in the control channel coincides with the identification symbol stored in the built-in memory. If it coincides as the judged result, namely, if it is located in the vicinity of the independent base station, it proceeds to a state of receiving the control channel of the independent base station. On the other hand, if it does not coincide as the judged result, namely, if it is located away from the independent base station, the location registration is carried out, and it proceeds to a waiting state of the control channel of the public base station.
Therefore, an object of the present invention is to provide a communication method of a cordless telephone that can always make a call as necessary and suppress an unnecessary waiting operation to reduce a consumption power, and a cordless telephone as the same.
The present invention has been made to solve the above-described problems of the conventional communication method of a cordless telephone and the cordless telephone. An object of the present invention is to provide a communication method of a cordless telephone that can always make a call as necessary and suppress an unnecessary waiting operation to reduce a consumption power, and a cordless telephone as the same.
In order to achieve an aspect of the present invention, a radio communication method includes (a) providing a mobile station which can make a call through each of an independent system base station and an outdoor public system base station, and (b) changing a period when a waiting operation to the independent system base station is performed, based on a distance between the mobile station and the independent system base station.
In this case, the (b) step includes stopping the waiting operation to the independent system base station, instead of the changing the period.
Also in this case, when a value of the distance is larger than a predetermined value, the (b) step includes making the period longer than that of a case that the distance value is not larger than the predetermined value.
Further in this case, the (b) step includes detecting the distance based on a receiving signal received by the mobile station from the outdoor public system base station adjacent to the independent system base station.
In this case, the (a) step includes providing a plurality of the outdoor public system base stations, and the outdoor public system base station adjacent to the independent system base station is one of the plurality of outdoor public system base stations which is positioned the closest to the independent system base station.
Also in this case, the (b) step includes changing the period, depending on whether the mobile station belongs to a specific region, wherein the specific region includes at least a part of a receiving region of the independent system base station and is wider than the at least a part of the receiving region of the independent system base station.
Further in this case, the specific region includes the receiving region of the independent system base station and a receiving region of the outdoor public system base station adjacent to the independent system base station.
In this case, the (b) step includes (c) judging in a first period as the period whether or not the mobile station belongs to a receiving region of the independent system base station as an independent receiving region, based on a receiving signal received by the mobile station, (d) detecting, as an unspecific outdoor public system base station, the outdoor public system base station, to whose receiving region the mobile station belongs, regardless of whether the mobile station belongs to the independent receiving region or not, (e) detecting, as a specific outdoor public system base station, the outdoor public system base station, to whose receiving region the mobile station belongs, when it is judged as a result of the (c) step that the mobile station belongs to the independent receiving region, (f) comparing the detected unspecific outdoor public system base station with the detected specific outdoor public system base station, (g) detecting the distance based on a result of the (f) step, (h) judging whether or not the detected distance is larger than a predetermined value, and (i) performing the (c) step in a second period longer than the first period when it is judged as the result of the (c) step that the mobile station does not belong to the independent receiving region and it is judged as a judgment result of the (h) step that the detected distance is larger than the predetermined value.
Also in this case, the (c) step includes judging that the mobile station belongs to the independent receiving region, when the receiving signal received by the mobile station has an independent system base station identification signal indicating that the receiving signal is transmitted from the independent system base station, the (d) step includes detecting the unspecific outdoor public system base station, based on an outdoor public system base station identification signal included in the receiving signal, indicating that the receiving signal is transmitted from the outdoor public system base station, and the (e) step includes detecting the specific outdoor public system base station, when it is judged that a first receiving signal corresponding to the receiving signal has the independent system base station identification signal as a result of the (c) step, based on the outdoor public system base station identification signal included in a second receiving signal received by the mobile station immediately after the first receiving signal.
Further in this case, the (e) step includes detecting the specific outdoor public system base station, based on the outdoor public system base station identification signal included in the receiving signal received next to the independent system base station identification signal by the mobile station.
In this case, the (e) step includes detecting the specific outdoor public system base station, based on the outdoor public system base station identification signal included in the receiving signal received in a same period as the period when the independent system base station identification signal is received.
Also in this case, the (f) step is performed each time the unspecific outdoor public system base station is detected as a result of the (d) step.
Further in this case, the radio communication method further includes (j) performing the (c) step in the first period, when it is judged as the result of the (c) step that the mobile station belongs to the independent receiving region or when it is judged as the result of the (h) step that the detected distance is not larger than the predetermined value, and when the (c) step is performed in the second period.
In this case, the (b) step includes (c) judging in a first period as the period whether or not the mobile station belongs to a receiving region of the independent system base station as an independent receiving region, based on a receiving signal received by the mobile station, (d) detecting, as an unspecific outdoor public system base station, the outdoor public system base station, to whose receiving region the mobile station belongs, regardless of whether the mobile station belongs to the independent receiving region or not, (e) detecting, as a specific outdoor public system base station, the outdoor public system base station, to whose receiving region the mobile station belongs, when it is judged as a result of the (c) step that the mobile station belongs to the independent receiving region, (f) comparing the detected unspecific outdoor public system base station with the detected specific outdoor public system base station, and (k) performing the (c) step in a second period longer than the first period when it is judged as the result of the (c) step that the mobile station does not belong to the independent receiving region and it is judged as a result of the (f) step that the unspecific outdoor public system base station and the specific outdoor public system base station do not coincide with each other.
Also in this case, the (b) step includes performing the (b) step for each the period.
In order to achieve another aspect of the present invention, a radio communication apparatus that can make a call through each of an independent system base station and an outdoor public system base station includes a timer for counting a time period during which a waiting operation to the independent system base station is performed, and a control section for controlling the timer such that the time period is changed in a accordance with a distance between the radio communication apparatus and the independent system base station.
In this case, the control section controls the timer such that the waiting operation is stopped, instead of controlling the timer such that the time period is changed.
Also in this case, when the distance is larger than a predetermined value, the control section controls the timer to make the time period longer than that of a case in which the distance is not larger than the predetermined value.
Further in this case, the control section detects the distance based on a receiving signal received by the radio communication apparatus from the outdoor public system base station adjacent to the independent system base station.
In this case, the control section changes the time period, depending on whether the radio communication apparatus belongs to a specific region, wherein the specific region includes at least a part of a receiving region of the independent system base station and is wider than the at least a part of the receiving region of the independent system base station.
Also in this case, the control section includes a judging means for judging as a specific judgment in a first period whether or not the radio communication apparatus belongs to a receiving region of the independent system base station as an independent receiving region, based on a receiving signal received by the radio communication apparatus, a first detecting means for detecting, as an unspecific outdoor public system base station, the outdoor public system base station, to whose receiving region the radio communication apparatus belongs, regardless of a result of the specific judgement, a second detecting means for detecting, as a specific outdoor public system base station, the outdoor public system base station, to whose receiving region the radio communication apparatus belongs, when the judging means judged that the radio communication apparatus belongs to the independent receiving region as the specific judgement, a comparing means for comparing the detected unspecific outdoor public system base station with the detected specific outdoor public system base station, a detecting means for detecting the distance based on a comparison result by the comparing means, a determining means for determining whether or not the detected distance is larger than a predetermined value, and a control means for controlling the judging means such that the judging means performs the specific judgment in a second period longer than the first period when the judging means judged that the radio communication apparatus does not belong to the independent receiving region and the determining means determined that the detected distance is larger than the predetermined value.
Further in this case, the judging means judges that the radio communication apparatus belongs to the independent receiving region, when the receiving signal received by the radio communication apparatus has an independent system base station identification signal indicating that the receiving signal is transmitted from the independent system base station, the first detecting means detects the unspecific outdoor public system base station, based on an outdoor public system base station identification signal included in the receiving signal, indicating that the receiving signal is transmitted from the outdoor public system base station, and the second detecting means detects the specific outdoor public system base station when the judging means judged that a first receiving signal corresponding to the receiving signal has the independent system base station identification signal, based on the outdoor public system base station identification signal included in a second receiving signal received by the radio communication apparatus immediately after the first receiving signal.
In this case, the control section includes a judging means for judging as a specific judgment in a first period whether or not the radio communication apparatus belongs to a receiving region of the independent system base station as an independent receiving region, based on a receiving signal received by the radio communication apparatus, a first detecting means for detecting, as an unspecific outdoor public system base station, the outdoor public system base station of which the radio communication apparatus belongs to a receiving region, regardless of a result of the specific judgment, a second detecting means for detecting, as a specific outdoor public system base station, the outdoor public system base station of which the radio communication apparatus belongs to a receiving region, when the judging means judged that the radio communication apparatus belongs to the independent receiving region as the specific judgment, a comparing means for comparing the detected unspecific outdoor public system base station with the detected specific outdoor public system base station to determine that the detected unspecific outdoor public system base station and the detected specific outdoor public system base station coincide with each other or not, and a control means for controlling the judging means such that the judging means performs the specific judgment in a second period longer than the first period when the judging means judged that the radio communication apparatus does not belong to the independent receiving region and the comparing means determined that the unspecific outdoor public system base station and the specific outdoor public system base station do not coincide with each other.
In order to achieve still another aspect of the present invention, a radio communication system includes an independent system base station, an outdoor public system base station, and a radio communication apparatus that can make a call through each of the independent system base station and the outdoor public system base station, wherein the radio communication apparatus includes a timer for counting a time period during which a waiting operation to the independent system base station is performed, and a control section for controlling the timer such that the time period is changed, in a accordance with a distance between the radio communication apparatus and the independent system base station.
In order to achieve yet still another aspect of the present invention, a computer readable recording medium for a recording a program for a process includes (c) judging as a specific judgment in a first period whether or not a mobile station belongs to a receiving region of an independent system base station as an independent receiving region, based on a receiving signal received by the mobile station, (d) detecting, as an unspecific outdoor public system base station, an outdoor public system base station, to whose receiving region the mobile station belongs, regardless of a result of the specific judgment, (e) detecting, as a specific outdoor public system base station, the outdoor public system base station, to whose receiving region the mobile station belongs, when it is judged as the result of the specific judgment that the mobile station belongs to the independent receiving region, (f) comparing the detected unspecific outdoor public system base station with the detected specific outdoor public system base station, and (j) performing the (c) step in a second period longer than the first period when it is judged as the result of the specific judgment that the mobile station does not belong to the independent receiving region and it is judged as a result of the (f) step that the unspecific outdoor public system base station and the specific outdoor public system base station do not coincide with each other.